The new Facebook chat behaves differently then normal chat programs. It shows not only online friends in the chat list but also all the other friends who are offline.
This is a very confusing features as there is no use of showing offline friends in the chat list. If you want to chat with a specific friend on Facebook, you need to first find out if he is online or offline by using the search box in the chat area.
Ideally, the Facebook chat box should show only online friends so that you can just look at the list and find out if someone is online or not.
I don’t know when Facebook will fix this issue, but you an fix it right now. Just install the Facebook Chat Fix Google chrome extension. This extension will make Facebook chat to show only online friends and hide offline friends.